Chalcopyrite, in a small but rich Ni-Cu-PGE deposit

--- Sudbury, Ontario, Canada

Figure 1.
Two small pieces of vein material, essentially massive chalcopyrite with
(invisible to the naked eye) platinum-group minerals and other species.
The piece on the left includes some of the host rock, cut at a sharp contact
by a vein. The sample on the right, representing a vein of visually pure chalcopyrite, was sawn, to enable the preparation of two polished mounts. Samples courtesy of Irwin Kennedy and Wanda Zyla.

"Rock of the Month #190, posted for April 2017" ---

Chalcopyrite -

globally the most important ore mineral of copper, forms in
numerous different geological environments, such as porphyry systems,
skarns, sedimentary deposits, and mafic-ultramafic melts.

History of the Occurrence

Broken Hammer was formerly part of the Wisner property, in Wisner township. It
lies in the east part of the North Rim, due north of Val Caron.
Chalcopyrite veins account for local high grades.
This little, short-lived mining enterprise
is well-documented. There is a location map (for the whole
Sudbury basin, Intierra / Northern Miner, 2008); geophysical
context (Balch, 2005); metallurgical test summary (Anon, 2006);
regional exploration (Keevil, 2014) and more.

The Broken Hammer and South Zone deposits in Wisner township lie in intensely brecciated zones of the footwall.
There are massive sulphide veins, disseminated or replacement sulphides, and quartz-dominated veins. Chalcopyrite is accompanied by
millerite and magnetite, pyrite, quartz and hydrous silicates such as actinolite. Discrete platinum-group mineral (PGM)
grains are often found as inclusions in sulphides and hydrous silicates. The PGM include tellurides typical of footwall deposits, such as merenskyite, michenerite and hessite, and also minerals uncommon at Sudbury, such as selenides: clausthalite, sopcheite, naumannite and bohdanowiczite.
Other minerals include violarite, wittichenite, melonite, tetradymite,
kotulskite and moncheite (Pentek et al., 2008).
In the wider context, the
ore mineralogy of sulphide ores from the footwall setting of the North Range
is dominated by chalcopyrite, but over 60 ore minerals are known.
In a recent study (Kjarsgaard and Ames, 2010) six deposits were sampled, in 3 settings, including veins at
the Levack footwall deposit, the McCreedy East mine
(see also Rock of the Month 115,
McCreedy West),
the 153 zone, and Broken Hammer.

Coarse, 10-20-mm sperrylite specimens, found in 2011, were sought by collectors (Wilson, 2012; Wilson, 2014, p.249; Moore, 2015, p.257; Moore, 2016, pp.515-516). Broken Hammer sperrylite is also featured in other publications (Paar et al., 2016).
The fine crystals are hosted in in chalcopyrite, epidote, or quartz plus epidote matrix (Wilson, 2012).
An introduction to a special issue of Canadian Mineralogist
(McDonald et al., 2011) has
a note on the naming of sperrylite, first discovered by Francis Lewis Sperry at the Vermilion mine in Denison township, near Sudbury:
the cover photograph features sperrylite from Broken Hammer.
Sperrylite, as an indicator mineral, has also been recovered from glacial
sediments, in till 250 m down-ice of the Broken Hammer zone
(McClenaghan et al., 2008; McClenaghan and Cabri, 2011).